1. Field of the Invention
The present invention relates to systems and methods for secure distribution of content and, more particularly, to a method and apparatus for distribution and synchronization of cryptographic context information in a video distribution system.
2. Description of the Background Art
Presently, programming providers desire the ability to deliver digital content to handheld mobile devices, such as cellular telephone, personal digital assistants (PDAs), and the like, in an effective manner. One standard for distributing digital content to handheld devices is the Digital Video Broadcasting (DVB) transmission system for handheld terminals (DVB-H), published by the European Telecommunications Standards Institute (ETSI). The DVB-H system is based on the terrestrial DVB system (DVB-T) for fixed reception of digital content. The DVB-H system is an end-to-end broadcast system for delivery of any type of digital content using Internet Protocol (IP)-based mechanisms optimized for devices with limitations on computational resources and battery (e.g., handheld mobile devices).
The DVB-H standard provides for digital rights management (DRM), which are a set of methods that ensures that a user device can only use particular content when relevant conditions (e.g., access conditions) have been met. Content is encrypted by a symmetric encryption algorithm using a key. Entitlement control messages (ECMs) are generated to securely transmit cryptographic context data to the devices. The cryptographic context data includes the keys used to encrypt the media stream, as well as other information necessary to decrypt and recover the content at the devices. The DVB-H standard, however, does not define an implementation for generating and distributing the ECMs. In particular, the DVB-H standard does not define how the functional unit that generates the ECMs obtains the cryptographic context data. The DVB-H standard also does not define how to synchronize the cryptographic context data with the encrypted content.
Accordingly, there exists a need in the art for a method and apparatus for distribution and synchronization of cryptographic context information in a DVB-H system.